DESCRIPTION: (Applicant's Abstract) The goal of this 5-year project is to evaluate the comparative effectiveness of the integrated and parallel models for organizing service delivery to dually-diagnosed individuals, within the environmental context of the Los Angeles County treatment systems for mental illness and substance abuse. A total of 400 subjects will be randomly assigned to receive either integrated treatment from outpatient mental health and residential drug treatment programs that jointly deliver dual-diagnosis treatment or concurrent mental health and residential drug treatment delivered by separate programs on a parallel basis. Primary treatment outcomes include retention and completion, service utilization, drug and alcohol use, psychiatric status, criminal behavior, and psychosocial functioning; secondary outcomes include physical health status, HIV risk, and housing status. The study will also identify client characteristics that influence treatment outcomes, either independently or in interaction with different models of service delivery, and examine the influence of program and staff characteristics on client outcomes. The treatment outcome study will be embedded within a study of the environmental context of the mental health and substance abuse treatment systems in Los Angeles County. Interviews will be conducted with county administrators, administrators of programs participating in the treatment outcome study, and administrators of programs that are not in the study for comparison purposes. In addition, surveys will be conducted with staff in these same programs. Focus groups will be conducted with members of key community stakeholder groups and changes in the mental health and substance abuse treatment service systems will be monitored throughout the study. These data will provide a multilevel context in which to evaluate the implementation and effectiveness of the two models of service delivery.